If you are using Windows XP, Microsoft has a patch that directly addresses this issue. Please go to the following link and download the Microsoft Patch for USB Isochronous Data Transfers Issues.
support.microsoft.com
If you are still experiencing the noise after you have downloaded and installed the patch, your computer may be using a USB chipset that is incompatible with USB audio. There are two types of USB protocols: Universal Host Controller Interface (UHCI) and Open Host Controller Interface (OHCI). Universal Host Controllers are generally solid when it comes to USB Audio. Open Host Controllers, however, have been known to exhibit certain incompatibilities. Note that there are no hard and fast rules, and every system is different.

To determine which type of chipset your computer is using, navigate to your computer's Device Manager and click on the "+" next to Universal Serial Bus Controllers. You'll see a listing that tells you which protocol, UHCI or OHCI, your computer is using. If your computer is using an Open Host controller and you are experiencing noise problems, it may be possible to eliminate the problem by using a PCI-based USB adapter with an Opti-chip controller. Be certain that the PCI USB adapter card you select is a Universal Host PCI (or PCHCI) card.